The invention relates to a hypocycloidal train mechanism for a vehicle seat including a brake with differential torque and anti-reversing properties.
Hypocycloidal train reducing mechanisms are used for vehicle seats in order to adjust either the sitting portion of the seat, or the inclination of its back portion in order to put the seat in a position corresponding favorably to the passenger's morphology.
But these mechanisms, despite the care taken during manufacture, include plays between : i) the toothings of the fixed and mobile flanges, and ii) the toothings of the double satellite driven by a cam. Accordingly, jerks during the operation of these mechanisms result, and these movements cause very rapidly unpleasant sensations for the passenger using the seat. When this phenomenon is examined, it is found that the satellite exhibits a tilting motion and rotates therefore in a jerky manner and faster than the cam.
WO-A-80/02677 shows a reducing device including two half cams with an interposed spring with a double spiral. The purpose is here to redoes the play between cam and satellite, which is not the object the present invention is concerned with.
In order to avoid reversibility, EP-A-O 099 549 shows placing a flexible buffer between the articulation operating knob, i.e. the cam, and a recess in the mobile flange of the seat back portion. In addition to the fact that it requires a direct intervention by the user's hand, this member does not provide for a sufficient braking of the mechanism since, at most, the cam is slightly braked.